This monkey carcinogenesis study, which was initiated in 1961, is in its final year. The phase-out plan is to complete the remaining studies and close the contract before the end of March, 1997. During the past decade, the major emphasis has been on the carcinogenic potential of dietary heterocyclic amines (HCA) which are found in cooked meat. The HCA carcinogenesis study was carried out in collaboration with scientists at the National Cancer Center Research Institute in Tokyo under the U.S.-Japan Cooperative Agreement. One of the three HCAs under investigation proved to be a potent hepatocarcinogen in cynomolgus monkeys. A decision was made to donate the last group of 36 monkeys, which belonged to the HCA program, to the Foundation of Cancer Research in Japan for continuation of the carcinogenesis study under a separate contract which was established at Corning Hazleton at no cost to NCI. Studies have been completed on monkeys dosed with cyclamate, saccharin and DDT for approximately twenty years. Sporadic cancer cases developed in older animals in all three groups, which are inconclusive of the carcinogenic potential of these compounds in nonhuman primates. There was however, evidence of testicular atrophy in monkeys dosed with cyclamate, as has been observed previously in rodents. A study on the effects of thalidomide on the development and progression of chemically-induced hepatocellular carcinomas is in the final stages. There is no evidence that thalidomide prevented the development or halted the growth of malignant liver tumors in these monkeys. The surviving breeders and other miscellaneous old animals, left in the monkey colony, are being used for the following short-term studies: tissue distribution of genomic and mitochondrial DNA incorporation for AZT, and adduct formation of tamoxifen and cisplatin (Dr. Poirier, LCCTP); isolation and characterization of vanilloid receptors from dorsal root ganglion cells.